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The distribution of benthic biomass in hadal trenches: a modelling approach to investigate the effect of vertical and lateral organic matter transport to the seafloor

The distribution of benthic biomass in hadal trenches: a modelling approach to investigate the effect of vertical and lateral organic matter transport to the seafloor
The distribution of benthic biomass in hadal trenches: a modelling approach to investigate the effect of vertical and lateral organic matter transport to the seafloor
Most of our knowledge about deep-sea habitats is limited to bathyal (200–3000 m) and abyssal depths (3000–6000 m), while relatively little is known about the hadal zone (6000–11,000 m). The basic paradigm for the distribution of deep seafloor biomass suggests that the reduction in biomass and average body size of benthic animals along depth gradients is mainly related to surface productivity and remineralisation of sinking particulate organic carbon with depth. However, there is evidence that this pattern is somewhat reversed in hadal trenches by the funnelling of organic sediments, which would result in increased food availability along the axis of the trenches and towards their deeper regions. Therefore, despite the extreme hydrostatic pressure and remoteness from the pelagic food supply, it is hypothesized that biomass can increase with depth in hadal trenches. We developed a numerical model of gravitational lateral sediment transport along the seafloor as a function of slope, using the Kermadec Trench, near New Zealand, as a test environment. We propose that local topography (at a scale of tens of kilometres) and trench shape can be used to provide useful estimates of local accumulation of food and, therefore, patterns of benthic biomass. Orientation and steepness of local slopes are the drivers of organic sediment accumulation in the model, which result in higher biomass along the axis of the trench, especially in the deepest spots, and lower biomass on the slopes, from which most sediment is removed. The model outputs for the Kermadec Trench are in agreement with observations suggesting the occurrence of a funnelling effect and substantial spatial variability in biomass inside a trench. Further trench surveys will be needed to determine the degree to which seafloor currents are important compared with the gravity-driven transport modelled here. These outputs can also benefit future hadal investigations by highlighting areas of potential biological interest, on which to focus sampling effort. Comprehensive exploration of hadal trenches will, in turn, provide datasets for improving the model parameters and increasing predictive power.
Hadal ecology, Sediment, Gravitational transport, Topography, Benthic biomass, Kermadec Trench
0967-0637
21-33
Ichino, Matteo I.
5b8c89ec-cefd-4280-b97d-23c2cb726702
Clark, Malcolm R.
cd47dc3e-9154-4ef9-a32f-d0e798c4e259
Drazen, Jeffrey C.
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Jamieson, Alan
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Jones, Daniel O.B.
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Martin, Adrian P.
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Rowden, Ashley A.
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Shank, Timothy M.
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Yancey, Paul H.
6c98b075-0716-4a42-9b04-2b7dd17a9e93
Ruhl, Henry A.
177608ef-7793-4911-86cf-cd9960ff22b6
Ichino, Matteo I.
5b8c89ec-cefd-4280-b97d-23c2cb726702
Clark, Malcolm R.
cd47dc3e-9154-4ef9-a32f-d0e798c4e259
Drazen, Jeffrey C.
554a715d-e0da-4732-9503-8de5b00da6af
Jamieson, Alan
0047b0a3-71dd-4d8a-8096-738d1ace0f85
Jones, Daniel O.B.
44fc07b3-5fb7-4bf5-9cec-78c78022613a
Martin, Adrian P.
9d0d480d-9b3c-44c2-aafe-bb980ed98a6d
Rowden, Ashley A.
b70b6061-f562-4346-bbab-13ddba40cde2
Shank, Timothy M.
bbd4cc25-0927-47ef-b514-29c8efc598fa
Yancey, Paul H.
6c98b075-0716-4a42-9b04-2b7dd17a9e93
Ruhl, Henry A.
177608ef-7793-4911-86cf-cd9960ff22b6

Ichino, Matteo I., Clark, Malcolm R., Drazen, Jeffrey C., Jamieson, Alan, Jones, Daniel O.B., Martin, Adrian P., Rowden, Ashley A., Shank, Timothy M., Yancey, Paul H. and Ruhl, Henry A. (2015) The distribution of benthic biomass in hadal trenches: a modelling approach to investigate the effect of vertical and lateral organic matter transport to the seafloor. Deep Sea Research Part I: Oceanographic Research Papers, 100, 21-33. (doi:10.1016/j.dsr.2015.01.010).

Record type: Article

Abstract

Most of our knowledge about deep-sea habitats is limited to bathyal (200–3000 m) and abyssal depths (3000–6000 m), while relatively little is known about the hadal zone (6000–11,000 m). The basic paradigm for the distribution of deep seafloor biomass suggests that the reduction in biomass and average body size of benthic animals along depth gradients is mainly related to surface productivity and remineralisation of sinking particulate organic carbon with depth. However, there is evidence that this pattern is somewhat reversed in hadal trenches by the funnelling of organic sediments, which would result in increased food availability along the axis of the trenches and towards their deeper regions. Therefore, despite the extreme hydrostatic pressure and remoteness from the pelagic food supply, it is hypothesized that biomass can increase with depth in hadal trenches. We developed a numerical model of gravitational lateral sediment transport along the seafloor as a function of slope, using the Kermadec Trench, near New Zealand, as a test environment. We propose that local topography (at a scale of tens of kilometres) and trench shape can be used to provide useful estimates of local accumulation of food and, therefore, patterns of benthic biomass. Orientation and steepness of local slopes are the drivers of organic sediment accumulation in the model, which result in higher biomass along the axis of the trench, especially in the deepest spots, and lower biomass on the slopes, from which most sediment is removed. The model outputs for the Kermadec Trench are in agreement with observations suggesting the occurrence of a funnelling effect and substantial spatial variability in biomass inside a trench. Further trench surveys will be needed to determine the degree to which seafloor currents are important compared with the gravity-driven transport modelled here. These outputs can also benefit future hadal investigations by highlighting areas of potential biological interest, on which to focus sampling effort. Comprehensive exploration of hadal trenches will, in turn, provide datasets for improving the model parameters and increasing predictive power.

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Accepted/In Press date: 7 February 2015
Published date: June 2015
Keywords: Hadal ecology, Sediment, Gravitational transport, Topography, Benthic biomass, Kermadec Trench
Organisations: Ocean and Earth Science, Marine Biogeochemistry

Identifiers

Local EPrints ID: 374500
URI: http://eprints.soton.ac.uk/id/eprint/374500
ISSN: 0967-0637
PURE UUID: 0f90130b-a231-4acf-a7f8-a367c96d391d

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Date deposited: 18 Feb 2015 09:43
Last modified: 27 Apr 2022 06:17

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Contributors

Author: Matteo I. Ichino
Author: Malcolm R. Clark
Author: Jeffrey C. Drazen
Author: Alan Jamieson
Author: Daniel O.B. Jones
Author: Adrian P. Martin
Author: Ashley A. Rowden
Author: Timothy M. Shank
Author: Paul H. Yancey
Author: Henry A. Ruhl

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